Organic light emitting diodes (OLEDs) are useful in a wide range of lighting applications, as well as high and low resolution display devices. They have been made both with low molecular-weight organic materials and with polymers. For full-color applications, it is necessary to have a set of red, green, and blue OLEDs. Efficient green and blue OLEDs are now available. Yet, there has been a lack of red OLEDs that exhibit both saturated emissions and high, stable luminescence quantum efficiency (Picciolo et al. (2001) Applied Phy. Lett. 78: 2378).
Currently, most red OLEDs contain dopant-containing layers made of red light emitting materials. See, e.g., Chen et al. (1997) Macromol. Symp. 125: 1; and Zhang et al. (2001) Chem. Mater. 13: 1565; and Picciolo et al. (2001) Appl. Phys. Lett. 78: 2378. The red light emitting materials can be polar, such as electron donor-substituted pyran compounds (Tang et al. (1989) Appl. Phys. Lett. 65: 3610; Zhang et al. (2001) Chem. Mater. 13: 1565; and Chen et al. (2001) J. Phys. D: Appl. Phys. 34: 30). They can also be extensively π-conjugated, such as porphyrin compounds (Burrows et al. (1996) Appl. Phys. Lett. 69: 2959; Morgado et al. (2001) J. Mater. Chem. 11: 278; and Kwong et al. (2000) Adv. Mater. 12: 1134). These materials have a tendency towards crystallization, and thus, are either weakly emissive or not emissive in solid state. Further, dopant-containing OLEDs are not favored in mass production.